​​​​We find strikingly robust evidence that semi-democracies are inherently less durable than both democracies and autocracies. “Semi-demo​cracies are particularly unstable political regimes” should thus be considered a rare stylized fact of comparative politics.

​Previous studies report that semi-democratic regimes are less durable than both democracies and autocracies. Still, mixing democratic and autocratic characteristics need not destabilize regimes, as three highly plausible alternative explanations of this correlation remain unaccounted for: (a) semi-democracies emerge under conditions of political inst​​ability and social turmoil; (b) other regime characteristics explain duration; and (c) extant democracy measures do not register all regime changes. We elaborate on and test for these explanations, but find strikingly robust evidence that semi-democracies are inherently less durable than both democracies and autocracies. “Semi-democracies are particularly unstable political regimes” should thus be considered a rare stylized fact of comparative politics. The analysis yields several other interesting results. For instance, autocracies and semi-democracies are equally likely to experience “liberalizing” regime changes more specifically, and once accounting for differences in degree of democracy, there is no robust evidence of differences in duration between military and single-party regimes.